Waterproofing a T&G roof

Discussion in 'Landscaping and Outdoors' started by Beattsmjk, Feb 20, 2015.

  1. Beattsmjk

    Beattsmjk New Member

    What's the best way to cover my summerhouse roof.

    I've just finished putting the roof on, it's 5m x 3m and is made up of 28mm thick T&G planks so is fairly substantial.

    There is a fall of 1 in 50 down the 5m length.

    I have been advised with it being T&G and therefore prone to movement I would need an underlay felt down first and them two layers of mineral felt on top.

    Is this overkill, would one layer of good felt properly fitted really not work? I don't want to bodge it but 3 layers of felt is going to be difficult to work with IMO, especially on the corners.
  2. No idea, but after all that work and such good quality materials, I personally wouldn't use out-dated felt...

    Surely the likes of EPDM would be FAR superior, and not much extra cost (if at all)?

    Especially if there's going to be movement; I believe felt is a bit prone to cracking when flexed - expanded and contracted.
    Last edited by a moderator: Feb 21, 2015
  3. Beattsmjk

    Beattsmjk New Member

    Yeah thanks, I was thinking of EPDM I'm just worried with it being T&G and EPDM being like 1.2mm thick, it will sit in the grooves between the boards if you know what I mean?
  4. You will need to ply over for a decent finish, the boards will show through the rubber.

    Put a perforated felt layer on first ( lightly tacked ) then I green mineral cap sheet, torch on.
  5. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    You've put the t&g with the groove(the dip the tongue makes) UP ?

    Mr. HandyAndy - Really
  6. Beattsmjk

    Beattsmjk New Member

    Mr HandyAndy.

    Not sure what you mean??

    The groove isn't up at all.

    The gap I refer to is the chamfer/ rounded edges on the boards where they butt together. The boards are laid flat there isn't an up side or a down side.

    Previous poster Cotswold thanks
  7. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Oh, so they are chamfered both sides?

    Mr. HandyAndy - Really
  8. Beattsmjk

    Beattsmjk New Member

    Yep Indeed.

    Even if they weren't they'd move about due to expansion / contraction.
  9. Beattsmjk

    Beattsmjk New Member

    I kinda knew that.


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